Two Stage Fm Transmitter

This Kit is a strong two quality, 9V FM transmitter (Tx) delay a adlawful of up to 1 kilometer in the notorious. It uses an RF transistor in its output quality. Distance of transmission is critically subject on the easy Conditions (in a edifice or out on the notorious), expression of aerial used (personal wire or dipole), easy voltage (12V is emend than 6V) and if the circumference is keen for ultimatum production. The kit is constructed on a personal-sided printed circumference toperative (PCB). It has a silk fence plaster on top to aid lection.On the foot tclose is a cement mask to acceleration in cementing. Protel Autotrax and Schematic were used to contrivance the consultation. ASSEMBLY INSTRUCTIONS Components may be adventitious to the PCB in any adjust. It is usually easier to add the latest apex components foremost then income to the taller components. The electret microphone should be inserted delay the pin united to the metal instance united to the denying reprove (that is, to the conclude or cipher voltage afterality of the circumference. ) This is remarkoperative delay a '-' memorial at the MIC on the circumference toperative printed plaster.To catch interinterroom all the resistors must be inserted established up on one end. Be attentive to get the transistors environing the set-right way. Note three tops: - the two 100n capacitors on the PCB keep 0. 2" and 0. 1" spacing. We keep put in components delay the set-right spacing for comfort of lection. - we keep gifted prewound, pre-soldered enamel 6 alter & 8 alter wire contortions. The legs should cement forthafter a suitableness to the pads of the PCB. However, pay eespecial regard to the cement flexure in instance all the enamel has not been oustd. You may keep to cement off or scratch off aggravate enamel from the ends of the two enamelled contortions. a affinity (or tap) is required from the average of the L1 tinned copper wire contortion to the pad remarkoperative TAP contiguous to the contortion. Cement a side of wire to the top of the average alter as shown on the plaster. Then cement the other end to the pad forthafter a suitableness contiguous to the L1 contortion. Disseminate out the contortions of L1 environing 1 mm partially. Make unfailing none of the loops of the contortion are affecting the loop contiguous to it. CIRCUIT DESCRIPTION The circumference is basically a radio abundance (RF) oscillator that operates environing 100 MHz. Audio choice up and amplified by the electret microphone is fed into the audio amplifier quality built environing the foremost transistor.Output from the collector is fed into the low of the assist transistor wclose it modulates the sonorous abundance of the tank circumference (L1 contortion and the red deckcap) by altering the joining capacitance of the transistor. Joining capacitance is a production of the germinative destruction applied to the low of the transistor T2. The tank circumference is united in a Hartley oscillator circumference. The decisive quality built environing T3 amplifies the output RF memorialal. Let us behold at the personal blocks of the circumference aggravate closely: The electret microphone: an electret is a enduringly full dielectric.It is made by heating a ceramic representative, placing it in a magnetic scope and then allowing it to remedioperative opportunity calm?} in the magnetic scope. It is the electrostatic equipollent of a enduring magnet. In the electret microphone a slice of this representative is used as part of the dielectric of a capacitor in which the diaphram of the microphone forms one compound. Sound presunfailing affects one of its compounds. The diversify-of-place of the compound diversifys the capacitance. The electret capacitor is united to an FET amplifier. These microphones are narrow, keep lawfulifioperative sensitivity, a expanded abundance reply and a very low absorb.First annotation quality: this is a plummet self-biasing sordid emitter amplifier. The 22n capacitor isolates the microphone from the low voltage of the transistor and solely allows alternating vulgar memorialals to ignoring. Oscillator quality: wrecess transmitter insufficiencys an oscillator to breed the RF carriage waves. The tank circumference, the transistor and the feedback capacitor are the oscillator circumference close. An input memorialal is not insufficiencyed to support the oscillation. The feedback memorialal makes the low-emitter vulgar of the transistor alter at the sonorous abundance.This causes the emitter-collector vulgar to alter at the selfselfcorresponding abundance. This memorialal fed to the aerial and radiated as radio waves. The call 'tank' circumference comes from the jurisdiction of the LC circumference to hoard courage for oscillations. In a sheer LC circumference (one delay no opposition) courage cannot be lost. (In an AC netproduction solely the resistive elements allure waste electrical courage. The sheerly reactive elements, the C and the L, lawful hoard courage to be returned to the rule after. ) Note that the tank circumference does not excite lawful by having a DC germinative put opposing it. Fixed feedback must be supposing. Deck Cap.The slots inlaterality the deck cap are modeld love the ruler of an arrow. The ultimatum capacitance prize is when the arrow is in notable to the 12 o'clock standing. A 180o alter brings the deckcap prize to its narrowness rated prize. Delay exemplificationation you allure be operative to plant up a toperative of wrecess capacitance prize (bear-in-mind to add in the 10pF) to FM abundance. You can besides diversify the abundance by altering the interinterroom among the contortions of L1. Disseminate out the L1 contortion expanded partially. The 10pF ceramic capacitor in correspondent delay the red deck cap allure enoperative you to air the Tx in the 98 MHz to 105 MHz adlawful of the retail FM ligature.If you use a remarkable prize (for pattern, 27pF) you allure affect the abundance down towards the other end of the FM ligature. This end generally has aggravate retail stations in it. Decisive Annotation Stage: this RF quality adds annotation to the RF memorialal. It insufficiencys an RF transistor to Kit 32. TWO STAGE FM TRANSMITTER do this efficiently. We use a Zetex ZTX320. L2 (an RFC radio abundance stifle) and the 10p capacitor in correspondent delay it are contrivanceed to bring harmonics from the circumference. Output jurisdiction from this quality allure be ultimatum when it is aird to excite at the selfselfcorresponding abundance as the antecedent quality.This can be commoditiesed delay the peaking circumference supposing and forcible partially beneath. A narrow (10pF) coupling capacitor on the aerial is optional to minimise the commodities of the aerial capacitance on the decisive quality LC circumference. (We keep not used one in this circumference. ) Dipole Antenna. Greater adlawful from the transmitter can be obtained by replacing the half-wave antenna (the diffusiveness of wire environing 160cm desire) delay a dipole antenna. This is basically two wires secure to two tops in the circumference which are uncertain 180o out of front delay each other.Two such tops are the antenna top and the fixed reprove (the +9V course. ) You can exemplification by piercing the antanna wire in half, leaving half cemented into the antenna top and cementing the otherhalf to the +9V pad. Top the two wires in facing directions. Easy Voltage. Output jurisdiction is besides extensiond by using a remarkable easy voltage. 9V is emend than 6V. The ultimatum easy voltage for this Kit is fixed by the ZTX320. This is 15V but if you try this then the prizes of some oppositions allure keep to diversify. You can exemplification delay this.WHAT TO DO IF IT DOES NOT WORK Poor cementing is the most lovely conclude that the circumference does not production. Restrain all cement flexures attentively underneathneath a good-tempered-tempered unsubstantial. Contiguous restrain that all components are in their set-right standing on the PCB. Did you add the affinity from the average of contortion L1 to the pad remarkoperative TAP? Restrain that the leads of the two contortions L2 and L3 are not dry flexures. Use a multimeter to restrain this. Restrain that you keep not accidently formed a cement affinity among two pads which are contiguous to each other. Did you alter the switch 'on'.Check that you did not interdiversify the 4K7 delay the 47K resistors. Is the ZTX320 environing the set-right way and in the T3 standing. Keep you unquestionably disseminate out the contortions of L1? Some fellow-creatures keep told us that each end of L1 should be bias aggravate and lawful environing affecting the PCB. They besides said that L3 should be disseminate partially a brief. See us at http://kitsrus. com COMPONENTS Resistors, 5%, 1/4W: 100R brown ebon brown 470R yellow violet brown 4K7 yellow violet red 22K red red oadlawful 39K oadlawful colorless oadlawful 47K yellow violet oadlawful 1M brown ebon bleak 1 1 1 1 1 2 1 Capacitors: Deck cap 5-20pF, red 1 5. pF ceramic 1 10p ceramic 2 47pF ceramic 3 1nF ceramic 1 20nF or 22nF ceramic 2 100nF monoblock 2 RF transistor ZTX320 1 Narrow memorialal transistor BC547 2 6 alter tinned copper contortion 1 6 alter enamelled contortion 1 8 alter enamelled contortion 1 9V battery split 1 Electret microphone 1 PCB-mounted SPDT switch 1 Antenna wire 1. 6m k32 PCB 1 Peaking circumference 1 packet of components Kit 32. TWO STAGE FM TRANSMITTER Peaking Circuit. Kit 32. The tank circumference - contortion L3 and the 47pF capacitor - insufficiencys to be aird in adlawful to get ultimatum jurisdiction output. It has to be aird to mate the abundance of the oscillator quality 10pF cap, varioperative capacitor and tapped L1 contortion.The output “peaks” as the tank circumference is aird to mate the oscillator abundance. This peak can be measured on a multimeter. A peaking circumference (shown beneath) is solely an RF guide that uses diodes to impute a capacitor. The voltage opposing the capacitor is measured using a voltmeter set to a low voltage adlawful (2 or 20V). The circumference can be assembled delayout the insufficiency of a PCB. Solely cement the components forthafter a suitableness to each other. The output (opposing C2) should be united forthafter a suitableness to the voltmeter input using banana plugs or a span of Nursing Dissertation clips bias to model.The input to the peaking circumference is cemented to the antenna wire recess on the PCB, using a 5cm (2”) diffusiveness of wire. Switch the voltmeter to the 2V or 20V DC adjust. To air the tank circumference, solely affect the alters of the tank contortion L3 further partially or closer concurrently until the lection on the voltmeter is a ultimatum. Note that the lection allure be inferior opportunity you are affecting the contortion. You allure closely positively confront that the contortion alters keep to be disseminate very far partially delay the latest alter at each end of the contortion closely affecting the PCB. Once the output is a ultimatum, reaffect the peaking circumference and associate the antenna.If you diversify the oscillator abundance by melting the deckcap then you allure insufficiency to reiterate the peaking proceeding in adlawful to get ultimatum jurisdiction output. Want Aggravate Range? You can get aggravate adlawful as a dealing off across stjurisdiction by: • bring R5 to 100R • bring R7 to 47R • incrcomfort C7 to 470pFor a re-examination of Kit 32 and abundant other FM transmitter kits on todays negotiate see: http://members. tripod. com/~transmitters/begin. htm To discover the embracing scheme following the production of two quality Fm Tx see: http://www. csn. ul. ie/~francis/fyp_report/